You have to get up very early in the morning to catch out Sir Paul Stephenson, the metropolitan police commissioner. Alternatively, you can just stay up late the night before. His attempt at dawn last Tuesday to arrest a burglar, aided only by a helicopter and 80 other officers in riot gear, was foiled by the dastardly Kingston upon Thames police who'd already arrested the suspect at 1.30am.

This would've been fine if the raid hadn't been a publicity exercise for the benefit of the London Evening Standard. "That's policing," said Sir Paul. No it isn't. It's PR and it's been cocked up. Everyone knows police commissioners don't personally arrest burglars. The aim was to raise Stephenson's profile with a dramatic demonstration of police effectiveness but what made the papers was a photo of enough men to take Quebec, all dressed up like the Rebel Alliance, miserably trudging home.

There was egg on all their faces even though none of them had remotely earned breakfast.

Photogenic criminals weren't the only thing that went missing last week. It also emerged that the British Library has mislaid 9,000 books (although to be fair, out of their 150 million items, it's only the equivalent of most libraries having the sex page torn out of Lady Chatterley's Lover). Most mysteriously of all, the Shropshire-based construction firm, the Wrekin Group, lost the Star of Zanzibar. At that point, even Sir Paul Stephenson should've sent for Sherlock Holmes (who is presumably currently working for Kingston CID).

Wrekin, apparently pronounced as in Wrekin havoc rather than Wrekin crew, but either is bang on, has recently gone into administration and it seems that one of its major assets is a ruby valued at £11m and known variously as the Star of Zanzibar and the Gem of Tanzania. It was acquired as part of a complicated deal in 2007 and allowed the company to declare a £3m surplus that year.

Its official accounts state that the jewel's value was certified at the Istituto Gemmologico Italiano (no translation prizes available here). The only problem was that it had disappeared.

"So where did you see it last?" asked the administrators, at which point the plot thickened when no one could recall having seen it at all, not even the Istituto, which was closed on the day the accounts claim that the stone was valued. "We have never seen a ruby that could be worth that much," was its verdict, which is not surprising since the most a ruby has ever fetched at auction is $3.62m, a fact I think I'd have googled before extending Wrekin any credit.

Maybe its creditors did but assumed that the company would need something heavy to stop all the bills and ring-road designs from blowing away. It worked better for the former than the latter. Let's be clear though. These builders are claiming to be in possession of an absolutely amazing ruby and yet a spokesman for the Tanzanian high commission said last week: "We do have a lot of rubies in Tanzania, but I've never heard of that one."

Well, my feeling was that we could stand Holmes down. There was no ruby. It was clearly a wheeze to make a virtual £11m to balance the company's books. And it would have worked perfectly if people hadn't actually started looking for the red shiny thing. If we could all have continued to believe in the ruby, then everything would have been fine. If we could've managed to believe in two, Wrekin would still be prospering.

A lot of plans like that are failing at the moment. From Bernard Madoff's assets to Pete Doherty's creativity, so many things are on the point of collapse because their keystones, the things on which they are predicated, have turned out not to exist. For ages all seems well. Madoff is the very image of a billionaire, Doherty of a pop star. Their plates are piled high with trimmings but underneath there's no turkey; there are hardly any investments, there's hardly any music.

It's easy to blame bankers for the economic crisis - and that's a perfectly good reason to do it - but we all believed in their ruby for too long. We took out loans we couldn't repay, we colluded in an economy driven by event organisers, PR companies and the buying and selling of complex financial instruments and smoothies. For a while, that seemed fine, but one day someone decided to check the safe and found it bare. It feels like we should have done that sooner or not at all.

People's basic needs are what they've always been: food and shelter. But there comes a point when you have to wonder whether Starbucks and construction firms only made solvent by undiscovered gemstones are the best way of providing them. Of course I don't really know what I'm talking about. I haven't a clue how a city like London, where I live, gets all its concrete and kebabs, particularly as no one I know makes either. I do a job which neither feeds nor shelters anyone, in exchange for which numbers are sent to me to add to my list of numbers (some people used to call these numbers "money") with which I can then buy food and shelter. I've never questioned it before. Now I'm scared.

But then on Friday, like a sunrise of hope, the Star of Zanzibar rose in the East or, rather, the Midlands. They found the ruby! It's more purple than red and as big as a cricket ball but sadly not worth anything like £11m. Brian Dunn, formerly of the Queen's jewellers, says the valuation is over-optimistic. And, as the gem previously appeared on another company's balance sheet valued at only £300,000, that seems likely. The ruby is a toxic asset but it does at least exist.

So when it comes to doom-laden metaphors for the credit crunch, I really should have taken the advice that many of you were kind enough to put in your online comments about last week's column: it just goes to show you can't be too careful.